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  <section id="checktypesize">
<span id="module:CheckTypeSize"></span><h1>CheckTypeSize<a class="headerlink" href="#checktypesize" title="Permalink to this heading">¶</a></h1>
<p>Check sizeof a type</p>
<dl class="cmake command">
<dt class="sig sig-object cmake" id="command:check_type_size">
<span class="sig-name descname"><span class="pre">check_type_size</span></span><a class="headerlink" href="#command:check_type_size" title="Permalink to this definition">¶</a></dt>
<dd><div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">check_type_size(</span><span class="nv">&lt;type&gt;</span><span class="w"> </span><span class="nv">&lt;variable&gt;</span><span class="w"> </span><span class="p">[</span><span class="no">BUILTIN_TYPES_ONLY</span><span class="p">]</span>
<span class="w">                                  </span><span class="p">[</span><span class="no">LANGUAGE</span><span class="w"> </span><span class="nv">&lt;language&gt;</span><span class="p">]</span><span class="nf">)</span>
</pre></div>
</div>
<p>Check if the type exists and determine its size.  Results are reported
in the following variables:</p>
<dl>
<dt><code class="docutils literal notranslate"><span class="pre">HAVE_&lt;variable&gt;</span></code></dt><dd><p>Holds a true or false value indicating whether the type exists.</p>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">&lt;variable&gt;</span></code></dt><dd><p>Holds one of the following values:</p>
<dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">&lt;size&gt;</span></code></dt><dd><p>Type has non-zero size <code class="docutils literal notranslate"><span class="pre">&lt;size&gt;</span></code>.</p>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">0</span></code></dt><dd><p>Type has architecture-dependent size.  This may occur when
<span class="target" id="index-0-variable:CMAKE_OSX_ARCHITECTURES"></span><a class="reference internal" href="../variable/CMAKE_OSX_ARCHITECTURES.html#variable:CMAKE_OSX_ARCHITECTURES" title="CMAKE_OSX_ARCHITECTURES"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_OSX_ARCHITECTURES</span></code></a> has multiple architectures.
In this case <code class="docutils literal notranslate"><span class="pre">&lt;variable&gt;_CODE</span></code> contains C preprocessor tests
mapping from each architecture macro to the corresponding type size.
The list of architecture macros is stored in <code class="docutils literal notranslate"><span class="pre">&lt;variable&gt;_KEYS</span></code>,
and the value for each key is stored in <code class="docutils literal notranslate"><span class="pre">&lt;variable&gt;-&lt;key&gt;</span></code>.</p>
</dd>
<dt>&quot;&quot; (empty string)</dt><dd><p>Type does not exist.</p>
</dd>
</dl>
</dd>
<dt><code class="docutils literal notranslate"><span class="pre">&lt;variable&gt;_CODE</span></code></dt><dd><p>Holds C preprocessor code to define the macro <code class="docutils literal notranslate"><span class="pre">&lt;variable&gt;</span></code> to the size
of the type, or to leave the macro undefined if the type does not exist.</p>
</dd>
</dl>
<p>The options are:</p>
<p><code class="docutils literal notranslate"><span class="pre">BUILTIN_TYPES_ONLY</span></code></p>
<blockquote>
<div><p>Support only compiler-builtin types.  If <em>not</em> given, the macro checks
for headers <code class="docutils literal notranslate"><span class="pre">&lt;sys/types.h&gt;</span></code>, <code class="docutils literal notranslate"><span class="pre">&lt;stdint.h&gt;</span></code>, and <code class="docutils literal notranslate"><span class="pre">&lt;stddef.h&gt;</span></code>, and
saves results in <code class="docutils literal notranslate"><span class="pre">HAVE_SYS_TYPES_H</span></code>, <code class="docutils literal notranslate"><span class="pre">HAVE_STDINT_H</span></code>, and
<code class="docutils literal notranslate"><span class="pre">HAVE_STDDEF_H</span></code>.  The type size check automatically includes the
available headers, thus supporting checks of types defined in the headers.</p>
</div></blockquote>
<dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">LANGUAGE</span> <span class="pre">&lt;language&gt;</span></code></dt><dd><p>Use the <code class="docutils literal notranslate"><span class="pre">&lt;language&gt;</span></code> compiler to perform the check.
Acceptable values are <code class="docutils literal notranslate"><span class="pre">C</span></code> and <code class="docutils literal notranslate"><span class="pre">CXX</span></code>.</p>
</dd>
</dl>
</dd></dl>

<p>Despite the name of the macro you may use it to check the size of more
complex expressions, too.  To check e.g.  for the size of a struct
member you can do something like this:</p>
<div class="highlight-cmake notranslate"><div class="highlight"><pre><span></span><span class="nf">check_type_size(</span><span class="s">&quot;((struct something*)0)-&gt;member&quot;</span><span class="w"> </span><span class="no">SIZEOF_MEMBER</span><span class="nf">)</span>
</pre></div>
</div>
<p>The following variables may be set before calling this macro to modify
the way the check is run:</p>
<blockquote>
<div><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_FLAGS</span></code></dt><dd><p>String of additional flags to pass to the compiler. The string must be
space-delimited--a <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> will not work.
The contents of <span class="target" id="index-0-variable:CMAKE_&lt;LANG&gt;_FLAGS"></span><a class="reference internal" href="../variable/CMAKE_LANG_FLAGS.html#variable:CMAKE_&lt;LANG&gt;_FLAGS" title="CMAKE_&lt;LANG&gt;_FLAGS"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_&lt;LANG&gt;_FLAGS</span></code></a> and
its associated configuration-specific variable are automatically added
to the compiler command before the contents of <code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_FLAGS</span></code>.</p>
</dd>
</dl>
</div></blockquote>
<blockquote>
<div><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_DEFINITIONS</span></code></dt><dd><p>A <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of compiler definitions of the form
<code class="docutils literal notranslate"><span class="pre">-DFOO</span></code> or <code class="docutils literal notranslate"><span class="pre">-DFOO=bar</span></code>. A definition for the name specified by
<code class="docutils literal notranslate"><span class="pre">&lt;resultVar&gt;</span></code> will also be added automatically.</p>
</dd>
</dl>
</div></blockquote>
<blockquote>
<div><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_INCLUDES</span></code></dt><dd><p>A <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of header search paths to pass to
the compiler. These will be the only header search paths used--the contents
of the <span class="target" id="index-0-prop_dir:INCLUDE_DIRECTORIES"></span><a class="reference internal" href="../prop_dir/INCLUDE_DIRECTORIES.html#prop_dir:INCLUDE_DIRECTORIES" title="INCLUDE_DIRECTORIES"><code class="xref cmake cmake-prop_dir docutils literal notranslate"><span class="pre">INCLUDE_DIRECTORIES</span></code></a> directory property will be ignored.</p>
</dd>
</dl>
</div></blockquote>
<blockquote>
<div><dl>
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_LINK_OPTIONS</span></code></dt><dd><div class="versionadded">
<p><span class="versionmodified added">New in version 3.14.</span></p>
</div>
<p>A <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of options to add to the link
command (see <span class="target" id="index-0-command:try_compile"></span><a class="reference internal" href="../command/try_compile.html#command:try_compile" title="try_compile"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">try_compile()</span></code></a> for further details).</p>
</dd>
</dl>
</div></blockquote>
<blockquote>
<div><dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_LIBRARIES</span></code></dt><dd><p>A <a class="reference internal" href="../manual/cmake-language.7.html#cmake-language-lists"><span class="std std-ref">;-list</span></a> of libraries to add to the link
command. These can be the name of system libraries or they can be
<a class="reference internal" href="../manual/cmake-buildsystem.7.html#imported-targets"><span class="std std-ref">Imported Targets</span></a> (see <span class="target" id="index-1-command:try_compile"></span><a class="reference internal" href="../command/try_compile.html#command:try_compile" title="try_compile"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">try_compile()</span></code></a> for
further details).</p>
</dd>
</dl>
</div></blockquote>
<blockquote>
<div><dl>
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_REQUIRED_QUIET</span></code></dt><dd><div class="versionadded">
<p><span class="versionmodified added">New in version 3.1.</span></p>
</div>
<p>If this variable evaluates to a boolean true value, all status messages
associated with the check will be suppressed.</p>
</dd>
</dl>
</div></blockquote>
<dl class="simple">
<dt><code class="docutils literal notranslate"><span class="pre">CMAKE_EXTRA_INCLUDE_FILES</span></code></dt><dd><p>list of extra headers to include.</p>
</dd>
</dl>
</section>


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